1. Field of the Invention
The following invention relates to stent-grafts for implantation into body lumens for support of the body lumens and to provide for repair and proper fluid flow through the body lumen. More particularly, this invention relates to stent-grafts which include anchors to keep the stent-grafts in a desired position, especially when implanted intraluminally, and most particularly to stent-grafts for intra-luminal implantation into the aortic artery of a human patient.
Stents are known in the surgical arts which are implanted intraluminally or otherwise and expanded to support the lumen and maintain fluid flow through the lumen. Such stents are often used in arteries where blood flow has become restricted with the stent propping the artery open to maintain proper fluid flow.
When an artery or other lumen becomes damaged, replacement of the damaged artery section with a graft may be indicated. Such grafts can be taken from other body lumens of the patient, or be in the form of an artificial prosthesis. Such grafts can replace a portion of the damaged artery or be implanted intraluminally or otherwise within the damaged section of the artery without removal of the damaged artery itself. The graft then supports blood flow within the damaged artery.
For grafts to function properly, they must be held in place where desired within the artery or other lumen. One technique for maintaining the proper position of the graft is to utilize a stent within a portion of the graft with the stent radially expanded to hold the portion of the graft adjacent the stent in position relative to the artery or other body lumen. Such a graft held in place by a stent can be provided as a single assembly for implantation, being then often referred to as a stent-graft. The stent can be coextensive with the graft or only provided at specific locations along the graft. The stent both acts to hold the graft in the desired position and also to maintain the desired open cross-section of the artery to maintain proper blood flow. When a graft is configured to both provide a substitute channel for flow of fluid through a body lumen and to keep the body lumen propped open, it can be referred to as a stent-graft also, even if it does not include a separate stent-like structure which is providing this support function.
One body lumen which is particularly suited to treatment of damage therein with a stent-graft is the aorta when it has developed an aneurysm. Such an aortic aneurysm can occur anywhere between the heart and the iliac arteries, resulting in an undesirable widening of at least a portion of the artery. Once such an aneurysm has formed, it is susceptible to rupture with a high probability of resulting mortality. It is known in the art to install a stent-graft in the aorta where the aneurysm exists. The stent-graft provides a new channel for blood flow through the region of the aneurysm, taking stress off of the arterial wall where the aneurysm exists so that the aneurysm will not rupture, and also channeling blood flow through the stent-graft so that even if the aneurysm were to rupture, internal bleeding would not result. The portion of the aorta which has the aneurysm therein can either be removed or remain in place if the stent-graft is delivered intraluminally or otherwise, within the portion of the aorta having the aneurysm.
One challenge presented by implantation of stent-grafts within the aorta is how to maintain the position of the stent-graft precisely where desired. It is desirable to avoid or minimize the need for suturing through the walls of the aorta so that the aorta walls can remain unpenetrated, and to avoid stressing the walls of the aneurysm by utilizing a stent which provides too great of radial pressure outward on the wall of the aorta. The relatively high blood flow and blood pressure existing within the aorta puts forces upon the stent-graft which present the possibility of dislodging the stent-graft from its desired position. Additionally, differing patient luminal geometries can cause a stent-graft which is well designed for an average patient to be either too large, too small or the wrong shape to be effectively held in place without damaging the aorta once implanted. Also, when the aneurysm is at a location on the aorta where a significant lateral artery is located, such as one of the renal arteries, one of the iliac arteries, or arteries extending off of the aortic arch, a typical prior art stent-graft will tend to block or limit flow to such lateral arteries, decreasing blood circulation to these portions of the patient, and decreasing the effectiveness of the procedure.
Accordingly, a need exists for implantable devices which can function effectively as a stent-graft and which can be placed within the aorta or other body lumens adjacent an aneurysm or other defect which will properly fit within the body lumen, avoid placing undesirable stress upon the body lumen, hold the stent-graft in the desired position and maintain blood flow to major lateral arteries off of the aorta, or other lateral lumens off of a primary lumen in which the device is implanted.